I saw what you need at Lowes in the electrical department. I have a walk in closet where I want to do the same thing but just haven't gotten to it yet.

What I saw at Lowes looks like you'll have to cut/notch a hole in the door jamb. I don't know if there are other easier switch types.

Another way of doing it, which is easier so long as your wall switch is located inside the pantry, is to change the switch to a motion detecting switch. That way the light goes on as soon as someone walks in, stays on while they are in the pantry, and you can adjust how quickly it goes off when they leave. I put one in our powder room and it works great. The one referred to above is typically used to turn lights on or off in a closet, but would certainly work also. The only downside (other than having to cut/drill the jamb and run the wires) is that if the door is not closed completely the light will remain on.

Funny you should mention this!
While in Lowes last night looking for the plunger switch (door jam switch) I noticed the motion sensors.

So that was the route I took. It is installed and working perfectly now and with much less hassle.

Thanks!
Joe